The 7mm Bergers do not expand to 2x diameter. They fragment into a cloud of metal, with only about 5% weight retention. That cloud fragmentation is what drops the elk on the spot.I don't know if this has anything to do with it, 13 of those elk were with the 35 Whelen AI. Using frontal area of a 2x diameter expanded bullet as a comparison (A=Pi x radius^2), it has 35% more frontal area than a .308 expanding to 2x diameter and 59% more than a 7mm projectile expanded to 2x diameter. The difference becomes more with a drop down in caliber. I have recovered (2) .358 Barnes mono's, both expanded to a bit more than double diameter across the petals. CNS function is disrupted as the bullet expands and travels through the animal. If a larger frontal diameter controlled expansion bullet causes disruption through the same principle of CNS disruption as a smaller caliber fast expanding bullet does, that could well be part of my positive experience with bullets that typically don't get credit for dropping animals quickly.